This invention relates generally to a modified pyrolysis type furnace construction for continuous removal of both solid and liquid organic contaminants from various metal parts and more particularly to having such modified furnace construction doing so in an improved and more effective manner.
In our earlier issued U.S. Pat. No. 4,970,969 there is described a novel batch type pyrolysis furnace for volatilizing and burning organic material from various metal parts which can thereafter be recycled for further use. This furnace apparatus employs a main combustion chamber operating at negative chamber pressure which is heated with an adjustable heating rate burner to directly heat air ducted into said main combustion chamber by convection heat transfer. A supplemental combustion chamber in open communication with said main combustion chamber and vented to the atmosphere contains an auxiliary burner to complete combustion of the volatilized organic contaminants being transported from the main combustion chamber. A single temperature sensing means disposed within said main combustion chamber together with water spray means responsive to said temperature sensing means cooperates with said adjustable heating rate burner to regulate operating temperatures within said main combustion chamber in accordance with a preselected heating schedule. Control of the furnace operation includes programmable temperature control means to maintain continuous operation of said adjustable heating rate burner with (i) a normal full supply of fuel necessary to maintain full combustion in the presence of excess oxygen during a major portion of the pyrolysis cycle, said excess oxygen being relative to the amount required to burn the fuel in said burner, and (ii) a diminished supply of fuel sufficient to maintain fuel-starved combustion during the final portion of the pyrolysis cycle, also in the presence of excess oxygen.
Our co-pending application Ser. No. 10/368,047 entitled xe2x80x9cPyrolysis Furnace Having Improved Heating Efficiencyxe2x80x9d and filed Feb. 14, 2003 which is also assigned to the present assigned, discloses novel heating means for said batch type pyrolysis furnace construction to provide both convection and radiant heating. The adjustable heating rate burner being employed in said furnace construction includes a tubular extension which combines convection heating with radiant heating during the furnace operation. There is again-further employed the same general type automated temperature control means for such improved furnace operation as was disclosed in our earlier issued patent. The entire contents of said referenced co-pending application are hereby specifically incorporated into the present application.
Batch type reclamation of contaminated metal parts in the foregoing manner has several recognized drawbacks. Material flow must be interrupted during processing in order to load the contaminated parts into the pyrolysis furnace as well as remove already cleaned parts therefrom. Higher labor costs are also attributable to such loading and unloading requirements. Further operator involvement to restart furnace operation with a new batch of the contaminated metal parts contributes to these higher labor costs. Energy costs will also be significantly higher with interrupted furnace operation. Such interrupted furnace operation can further require greater operator involvement for control of the pyrolysis process in order to avoid damaged or unclean metal parts being produced.
As distinct therefrom, continuous furnace operation enables a more effective control of the pyrolysis cycle with lower operating costs. Higher material throughput can be achieved in this manner with minimal operator involvement. Reduced scrap material can also be realized with continuous furnace operation due to much improved control of the pyrolysis cycle being carried out. Start up and cool down periods are thereby eliminated with continuous furnace operation employing conventional equipment means to supply and remove material to the already heated furnace. Thus, a wide variety of contaminated parts can be reclaimed in a continuous manner, including parts contaminated with coatings, lubricants or cutting fluids.
It is an important object of the present invention, therefore, to provide a more effective means to remove organic contaminants from metal parts in a pyrolysis furnace.
It is another important object of the present invention to provide a continuous feed-type pyrolysis furnace adapted for reclamation of contaminated metal parts.
Still another important object of the present invention is to provide a continuous operation pyrolysis furnace incorporating novel structural means for removing organic contaminants from metal parts.
Still another important object of the. present invention is to provide a novel method for continuous removal of organic contaminants from metal parts in a pyrolysis furnace.
These and still further object of the present invention will become more apparent upon considering the following more detailed description of the present invention.
It has now been discovered, surprisingly, that removal of organic contaminants from metal parts can be carried out more effectively and in a continuous manner when processed in the presently modified furnace apparatus. More particularly, the processing procedure of the present invention employs a pyrolysis furnace having an enclosure physically divided into a main combustion chamber connected to inlet and exhaust chambers, a rotating retort vessel extending thru said enclosure to enable continuous passage of the contaminated metal parts thru said furnace enclosure, an adjustable heating rate burner to directly heat air ducted into said enclosure, and multiple supplemental combustion chambers in open communication with said furnace enclosure and vented to the atmosphere with each containing an auxiliary burner. In said operating procedure, the main combustion chamber is operated with a single temperature sensing means in combination with control means including programmable temperature control means to maintain continuous operation of said adjustable heating rate burner with (i) a normal fuel supply necessary to maintain full combustion of said organic contaminants in the presence of excess oxygen during a major portion of the pyrolysis cycle, said excess oxygen being relative to the amount required to burn the fuel in said burner, and (ii) a diminished supply of fuel sufficient to maintain fuel-starved combustion during the final portion of the pyrolysis cycle, also in the presence of excess oxygen. Water spray means are actuated within said furnace enclosure responsive to said temperature sensing means for operative cooperation with said adjustable heating rate burner to regulate operating temperatures within said furnace enclosure in accordance with a preselected heating schedule. A typical temperature control procedure regulates operating temperature in said furnace enclosure in small incremental stages so as not to exceed a maximum temperature set point. A suitable retort vessel for use in the present furnace construction desirably extends thru said furnace enclosure while being vented to enable exhaust of the volatilized organic contaminants into all divided chambers. Said retort vessel is further provided with inner protuberances, such as flight having a helical configuration, to assist with continuous transport of the contaminated metal parts upon admission to said rotating furnace member. During furnace operation in accordance with the present invention, the main combustion chamber operates at positive chamber pressure whereas both inlet and exhaust chambers in the furnace enclosure are maintained at a negative chamber pressure as are the supplemental combustion chambers in open communication with said furnace enclosure. Pressure sensing means, such as manometers and the like, can also be included in the present furnace construction to monitor desired chamber pressure conditions during furnace operation.